Conventional methods for obtaining a hydrocarbon such as methane by reducing carbon dioxide include a method described in Patent Document 1 in which hydrogen gas is used as a hydrogen source under the reaction condition of a high temperature (150° C. to 400° C.) and a high pressure (1 MPa to 6 MPa). However, this method requires such a reaction condition of a high temperature and a high pressure, and thus the reaction equipment becomes complicated, leading to high cost, for example.
In contrast, as a method that is conducted under the condition of an ordinary temperature and an ordinary pressure and requires no hydrogen gas as a hydrogen source, Patent Document 2 describes a method that uses iron powder as a catalyst to obtain a hydrocarbon such as methane from carbon dioxide and water.
Although methods described in Patent Documents 3 and 4 produce hydrogen from particulate magnesium and water, these methods are not for obtaining a hydrocarbon such as methane by reducing carbon dioxide.